Jellyfish, cockroaches of ocean, set off climate alarm

August 3, 2008|By Elisabeth Rosenthal, The New York Times

BARCELONA, Spain -- Blue patrol boats crisscross the swimming areas of beaches with their huge nets skimming the water's surface. The yellow flags that urge caution and the red flags that prohibit swimming because of risky currents are sometimes topped with blue ones warning of a new danger: swarms of jellyfish.

In a period of hours a couple of weeks ago, 300 people on Barcelona's bustling beaches were treated for stings, and 11 were taken to hospitals.

From Spain to New York, to Australia, Japan and Hawaii, jellyfish are becoming more numerous and more widespread, and they are showing up in places where they have rarely been seen before, scientists say. The faceless marauders are stinging children blithely bathing on summer vacations, forcing beaches to close and clogging fishing nets.

While jellyfish invasions are a nuisance to swimmers and a hardship to fishermen, for scientists they are a source of more profound alarm, a signal of the declining health of the world's oceans.

The explosion of jellyfish populations, scientists say, reflects a combination of severe overfishing of natural predators, such as tuna, sharks and swordfish; rising sea temperatures caused in part by global warming; and pollution that has depleted oxygen levels in coastal shallows.

Jellyfish in fact are the cockroaches of the open waters, the ultimate maritime survivors who thrive in damaged environments, and that is what they are doing.

Though no good global database exists on jellyfish populations, increasing reports from around the world have convinced scientists that the trend is real, serious and climate-related, although they caution that jellyfish populations in any one place undergo year-to-year variation.